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Lecture

Laser Sintering and Melting: Thermal Properties and Intensity

In course

ME-413: Introduction to additive manufacturing

The state of the art in the domain of additive production processes (the part is built by material addition without use of a shape tool) will be presented. The main application/benefits/shortcomings of the common additive processes as well as technologi ...

Description

This lecture covers the consolidation mechanism in selective laser sintering and melting, the needed laser intensity, heat diffusion in a powder bed, absorption coefficient, thermal and electrical conductivity, and the graphical representation of H functions. It also discusses the minimal intensity required for metal selective laser sintering, focusing of thermal/fluorescent sources, and the expected intensity after focalization.

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Instructors (3)

Eric Boillat

Jürgen Brugger

I am a Professor of Microengineering and co-affiliated to Materials Science. Before joining EPFL I was at the MESA Research Institute of Nanotechnology at the University of Twente in the Netherlands, at the IBM Zurich Research Laboratory, and at the Hitachi Central Research Laboratory, in Tokyo, Japan. I received a Master in Physical-Electronics and a PhD degree from Neuchâtel University, Switzerland. Research in my laboratory focuses on various aspects of MEMS and Nanotechnology. My group contributes to the field at the fundamental level as well as in technological development, as demonstrated by the start-ups that spun off from the lab. In our research, key competences are in micro/nanofabrication, additive micro-manufacturing, new materials for MEMS, increasingly for wearable and biomedical applications. Together with my students and colleagues we published over 200 peer-refereed papers and I had the pleasure to supervise over 25 PhD students. Former students and postdocs have been successful in receiving awards and starting their own scientific careers. I am honoured for the appointment in 2016 as Fellow of the IEEE “For contributions to micro and nano manufacturing technology”. In 2017 my lab was awarded an ERC AdvG in the field of advanced micro-manufacturing.

Christophe Moser

Dr. Christophe Moser is Associate Professor of Microengineering and Industrial Relations at the Swiss Federal Institute of Technology in Lausanne. He was the co-founder and CEO of Ondax,Inc for ten years prior to joining EPFL. During this decade, he raised $15 million from corporate and venture capital sources to fund volume production of thick holographic components in glass and develop devices enabled by these components such as tunable add-drop multiplexers for telecommunications, ultra-narrowband notch filters for low frequency Raman systems, high power semi-conductor frequency-narrowed pumps for fiber lasers, single frequency fixed and tunable lasers for sensing and femtosecond pulse compressors for micro-machining applications. Dr. Moser has a Ph.D. in Electrical Engineering from the California Institute of Technology, a minor in finance and a bachelor degree in Physics from EPFL. He is the co-inventor of 24 patents, 14 peer reviewed scientific publications, 9 IEEE proceedings and a book chapter. Private interests include tennis, running, ski, basketball and family excursions. 2010: Associate Professor, EPFL, faculty Science Technique Ingenieur. 2000-2010: co-founder, CEO Ondax, Inc. 1995-2000: Graduate Research Assistant, California Institute of Technology. 1993-1995: Engineering Project manager , TESA. 1988-1993: Bachelor candidate in Physics, EPFL. MAIN PUBLICATIONS:

Moser C., Havermeyer F,.Ultra-narrowband tunable laserline notch filter, Appl. Phys. B, 95 (3), pp 597-601, 2009.

Moser C. ,Ho L., Havermeyer F,. Self-aligned Non-dispersive External Cavity Tunable Laser, 16 (21), 16691-16696 Optics Express, 2008.

Steckman, GJ , Moser C. et al. Volume holographic grating wavelength stabilized laser diodes, IEEE J. Of Selected Topics in Quantum Electronics, (13), 672-678, 2007.

Buse K, Havermeyer F, Liu W., Moser C, Psaltis D. Holographic Filters , Book Chapter Photorefractive Materials and their Applications, 2005.

Havermeyer, F; Liu, WH; Moser, C, et al. Volume holographic grating-based continuously tunable optical filter , Opt. Eng. 43 (9), 2017-2021, 2004.

Moser C., Maravic I., Schupp B., Adibi A, Psaltis D, Diffraction efficiency of localized holograms in doubly doped LiNbO3 crystals, Opt. Lett. 25: (17),1243-1245, 2000.

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Related concepts (32)

Thermal conductivity

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by , , or . Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like mineral wool or Styrofoam.

Thermal insulation

Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials. Heat flow is an inevitable consequence of contact between objects of different temperature.

Thermal conduction

Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its thermal conductivity, and is denoted k. Heat spontaneously flows along a temperature gradient (i.e. from a hotter body to a colder body). For example, heat is conducted from the hotplate of an electric stove to the bottom of a saucepan in contact with it.

Sintering

Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The nanoparticles in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece.

Thermal resistance

Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. (Absolute) thermal resistance R in kelvins per watt (K/W) is a property of a particular component. For example, a characteristic of a heat sink. Specific thermal resistance or thermal resistivity Rλ in kelvin–metres per watt (K⋅m/W), is a material constant.

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